Ensure small sleeps are accurate through a context switch.

Change-Id: Ie4efdf83d3baee1526f786a78118022baa67a73a
Reviewed-on: http://gfw160.aus.stglabs.ibm.com:8080/gerrit/9052
Tested-by: Jenkins Server
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>
Reviewed-by: Douglas R. Gilbert <dgilbert@us.ibm.com>
Reviewed-by: A. Patrick Williams III <iawillia@us.ibm.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/src/kernel/timemgr.C b/src/kernel/timemgr.C
index 39cb4b807..37d258029 100644
--- a/src/kernel/timemgr.C
+++ b/src/kernel/timemgr.C
@@ -26,6 +26,8 @@
 #include <kernel/task.H>
 #include <kernel/cpumgr.H>
 #include <util/misc.H>
+#include <kernel/misc.H>
+#include <sys/task.h>
 
 uint64_t TimeManager::iv_timebaseFreq = 0xFFFFFFFF;
 
@@ -154,6 +156,17 @@ bool TimeManager::simpleDelay(uint64_t i_sec, uint64_t i_nsec)
     uint64_t threshold = getTimeSliceCount()/YIELD_THRESHOLD_PER_SLICE;
     uint64_t delay = convertSecToTicks(i_sec, i_nsec);
 
+    bool isUserspace = !KernelMisc::in_kernel_mode();
+
+    // TB is not synchronized between cores, so if we're doing a poll we need
+    // to pin the task to the current cpu.  Otherwise the getTB can get a
+    // drifted answer after a task migration.
+    if (isUserspace)
+    {
+        task_affinity_pin();
+    }
+
+    // Do polling delay.
     if(delay < threshold)
     {
         uint64_t expire = getCurrentTimeBase() + delay;
@@ -165,6 +178,11 @@ bool TimeManager::simpleDelay(uint64_t i_sec, uint64_t i_nsec)
         result = true;
     }
 
+    if (isUserspace)
+    {
+        task_affinity_unpin();
+    }
+
     return result;
 }